American researchers are finally getting a real-time view inside one of the most unforgiving propulsion systems in service, the solid-fuel ramjet, and the payoff could be missiles that fly farther on the same fuel load and stay lethal deep into contested airspace. By peering into the combustion heart of these engines, U.S. teams say they can tune performance so precisely that operational range may effectively triple compared with today’s conventional rocket-powered weapons. I see that work as the missing link between headline-grabbing test shots and a mature class of long-range missiles, artillery shells, and potentially aircraft that rely on ramjets as a routine part of modern warfare.
Seeing inside a brutal engine
The solid-fuel ramjet has always been a paradox, promising extraordinary range and speed while remaining largely opaque to the engineers trying to perfect it. At the U.S. Naval Research Laboratory, Scientists have now used advanced optical diagnostics to look directly into the combustion zone of working engines, capturing how the solid fuel surface reacts as supersonic air rips through the chamber and ignites. That work, described by NRL and expanded in a separate report by Young for Military Ja, turns what used to be guesswork based on exhaust measurements into a high-speed movie of flame fronts, pressure waves, and fuel regression.
In parallel, a detailed account from the Naval Research Laboratory explains how these breakthroughs in testing are giving engineers a way to correlate what they see with thrust, pressure, and temperature data. Copy Link notes that Scientists at the Naval Research Laboratory are building a next generation of solid-fuel ramjet propulsion that uses the incoming air as the oxidizer, which slashes the mass of onboard propellant and opens the door to much longer range. By tying optical diagnostics to these test campaigns, the lab is effectively building a design playbook for how to shape fuel grains, inlets, and nozzles so that the engine stays stable even as it endures extreme heating and pressure spikes.
How solid-fuel ramjets stretch range
At the core of the range story is a simple physics advantage: a solid-fuel ramjet carries only fuel, not oxidizer, and relies on high-speed airflow to complete the combustion mix. In the U.S.–Norwegian program highlighted in Oct reporting By John A. Tirpak, the solid fuel is formulated so it sublimates into the airstream and burns as it mixes, which allows the missile to sustain thrust long after a traditional rocket would have gone ballistic. That joint effort with Norway has already passed a series of speed and range tests, validating that the concept works outside the lab.
The same logic is driving U.S. flight experiments described in a separate account of how Washburn and colleagues are refining range, endurance, and targeting. Washburn highlights that this is a combat-credible technology and notes that the team is working to push the envelope of how far a ramjet missile can fly while still maneuvering aggressively at the endgame, according to some previous experiments. A companion passage in the same report stresses that Solid Fuel Ramjet technology is not new, and that The Solid Fuel Ramjet has been explored for decades. However, the same source argues that it is only now becoming a practical solution for the fleet today, as guidance, materials, and test infrastructure catch up with the raw promise of the engine.
THOR-ER and the U.S.–Norway proving ground
If the lab work is the microscope, the THOR-ER program is the wind tunnel and firing range rolled into one. About the THOR effort, a detailed project history explains that About the THOR Extended Range (THOR-ER) project, the U.S. Department of Defense and the Norwegian Ministry of Defense created a joint framework to mature solid-fuel ramjet missiles for operational use. In April, that partnership was formalized as the Department of Defense and the Norwegian Ministry of Defense announced a shared roadmap that would leverage the Norwegian industry partner Nammo’s experience with high energy propellants and air-breathing inlets. The same account notes that the Norwegian industry partner Nammo is central to the design and testing work, providing a rare example of deep transatlantic cooperation on cutting-edge propulsion.
The THOR-ER team has since completed a historic ramjet missile test that demonstrated stable combustion and guidance throughout a demanding flight profile, according to the In April program summary. That success dovetails with the Oct test campaign described by Oct
From missiles to artillery shells and combined-cycle weapons
Ramjet propulsion is no longer confined to sleek anti-ship missiles skimming over the ocean. In the artillery world, a quiet revolution is underway as engineers adapt similar engines to 155 mm shells that can fly far beyond traditional gun ranges. A detailed explainer on the Ramjet 155 concept describes how a projectile can use a compact air intake and solid fuel grain to sustain thrust out to roughly 150 km, a point underscored in a video released in Sep. That same theme appears in a report on NATO’s New Super Shell, which notes that Ramjet Artillery Can Strike 150km With Pinpoint Accuracy. In that account, NATO’s New Super Shell is being developed by American defense giant Boeing and Norway-based partners, with the explicit goal of giving ground forces a way to hit high value targets deep behind the front line With Pinpoint Accuracy.
At the same time, industry is pushing ramjets into more complex propulsion architectures that blend rockets, turbines, and air-breathing engines. A recent concept from Lockheed describes a missile with a ramjet engine and combined-cycle propulsion designed to offer a 620-mile range, a figure that would have been unthinkable for a tactical weapon a generation ago. The same report notes that An American weapon manufacturer recently displayed the system at an annual convention, with observers highlighting how a dual mode motor could let the missile accelerate through different flight regimes while staying difficult to intercept. In my view, that kind of architecture is where the Naval Research Laboratory’s combustion movies and the THOR-ER team’s flight data will matter most, because combined-cycle engines are unforgiving of instability at any point in the envelope.
From lab curiosity to combat staple
What ties these threads together is a shift from treating ramjets as exotic one-off experiments to integrating them into mainstream force planning. The Naval Research Laboratory’s own summary of its work, published under the heading Copy Link, makes that point explicitly by framing solid-fuel ramjets as a way to produce thrust using the air rather than carrying oxidizer. That framing aligns with the earlier description of Scientists at the Naval Research Laboratory who are developing the next generation of solid-fuel ramjet propulsion to support a range of missions, from long-range strike to missile defense. When I look at those efforts alongside the U.S.–Norwegian tests and NATO’s artillery experiments, the pattern is clear: air-breathing solid-fuel engines are being treated as a foundational technology, not a science project.
The same evolution shows up in how operational testers talk about the weapons. In the U.S. flight trials described by Washburn, the emphasis is on combat credibility, not just technical novelty, with planners already thinking about how to refine range, endurance, and targeting for real-world missions. A related passage in the same account underscores that However mature the basic physics may be, the surrounding ecosystem of guidance, materials, and test data is what finally makes Solid Fuel Ramjet weapons a solution for the fleet today. With NRL’s optical diagnostics turning the inside of the engine from a black box into a measurable, optimizable system, the idea of tripling missile range is no longer a speculative claim. It is a design target that engineers can see, frame by frame, as they push these brutal engines toward everyday use in U.S. and allied arsenals.
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